import java.util.*;
public class _acw4794 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt();
        int a[]={0,0,0};
        String b[]={"chest","biceps","back"};
        for(int i=0;i<n;i++){
            a[i%3]+=sc.nextInt();
        }
        if(a[0]>a[1]&&a[0]>a[2]){
            System.out.println(b[0]);
        }
        if(a[1]>a[0]&&a[1]>a[2]){
            System.out.println(b[1]);
        }
        if(a[2]>a[1]&&a[2]>a[0]){
            System.out.println(b[2]);
        }

    }
}
